From Big Medical Encyclopedia

DIAPAUSE (Greek diapausis having rummaged, a stop) — the period fiziol. rest in development of some animal species. D.'s approach is followed by sharp increase of resistance of an organism to adverse environmental factors (including and to action of various insecticides).

Is the cornerstone falloff of intensity fiziol, the processes connected with development or reproduction, caused by change-type of a metabolism. Owing to decrease in intensity of exchange processes the economical expenditure deposited in bodies and fabrics of reserve substances (carbohydrates, fats, proteins) that allows an organism to endure the adverse period is reached. D.'s condition is followed by dehydration of fabrics. Historically D. arose as a result of adaptation to seasonal frequency of abiotic factors of the environment, at a cut the periods favorable for active life alternate with adverse. The winter dormancy (hibernation) providing increase in frost resistance and a wintering of organisms is widespread in moderate and northern latitudes. In the conditions of droughty climate summer D. (so-called aestivation) promoting experience of individuals during the droughty periods of year when there is no enough water and food is observed.

In each of these two main directions of adaptive evolution of animals allocate 4 modifications of the prospective rest (forming before unfavorable conditions): a dream — the most general and eurysynusic phenomenon of periodic rest; an oligopauza — a condition of rather superficial rest; actually D. — a condition of true and long dormancy; a superpause — D.'s condition lasting over a year.

At different types of D. it can be shown at different stages and stages of an ontogeny. Distinguish embryonal D. (a dormant period at a stage of egg between fertilization and crushing or upon termination of crushing; it is observed at rotifers, insects, some rodents, predatory etc.); larval D. or kukolochny (at some butterflies wintering at a stage of a doll in the soil or on trees) and imaginal D. (it is observed at some mosquitoes, bugs leaf beetles and some other insects, at a cut mobility of an animal can remain, but maturing of reproductive products stops). At one types end of a life cycle is impossible without D. (obligate D.) owing to what they give only one generation a year. At others development of several generations is possible without D. and only at approach of unfavorable conditions in the environment there comes D. (optional D.).

By it is fixed hereditarily as the reaction norm which is shown depending on environmental conditions. Due to the universality fiziol, mechanisms D. and its modifications and their high lability under the corresponding conditions winter D. can pass in summer, long-term and back.

See also Biological rhythms .

R. S. Ushatinskaya.